One known type of information storage device is a disk drive device that uses magnetic media to store data and a movable read/write head that is positioned over the media to selectively read data from or write data to the media.
FIG. 1a illustrates a typical disk drive device 2. A magnetic disk 201 is mounted on a spindle motor 202 for spinning the disk 201. A voice coil motor arm 204 carries a head gimbal assembly (HGA) 200 that includes a slider 203 incorporating a read/write head and a suspension 213 to support the slider 203. A voice-coil motor (VCM) 209 is provided for controlling the motion of the motor arm 204 and, in turn, controlling the slider 203 to move from track to track across the surface of the disk 201. In operation, a lift force is generated by the aerodynamic interaction between the slider 203 and the spinning magnetic disk 201, such that the voice coil motor arm 204 maintains a predetermined flying height above the surface of the magnetic disk 201.
FIG. 1b shows a perspective view of the slider of FIG. 1a. As illustrated, the slider 203 includes a substrate 219 which constitutes main body thereof. An air-bearing surface (ABS) 217 is defined on one surface of the substrate 219. Besides, a read/write head 216 is formed on the ABS 217 adjacent one edge of the substrate 219. In the industry, the ABS 217 is formed on the substrate 219 by photolithography and etching process and this will be described below.
Referring to FIG. 2a, at first, the substrate 219 is coated with a layer of photo-resist 26 on its top surface 240 via a dispenser 20. Then, the photo-resist 26 covered on the substrate 219 is exposed to a light beam 21 through ABS pattern holes 282 of a photo-mask 28, such that ABS pattern is accurately transferred to the photo-resist 26 (exposed regions 262 formed on the photo-resist 26 collectively constitute the ABS pattern), as shown in FIG. 2b. Next, as shown in FIG. 2c, the substrate 219 along with the photo-resist is baked for a period of time so that polymerization reacts sufficiently. After that, a developing procedure is implemented so as to remove the exposed regions away from the photo-resist 26, thereby trenches 270 being defined in the photo-resist 26 and partial material of the substrate 219 at the top surface 240 being exposed outside from these trenches 270, as shown in FIG. 2d. Finally, as shown in FIG. 2e, ion-milling or reactive ion etching process is performed to remove partial material of the substrate 219 exposed outside from the trenches 270 at the top surface 240, thus recesses 25 being formed on the top surface 240 of the substrate 219. These recesses 25 collectively define an ABS on the substrate 219. At last, the residual photo-resist 26 is stripped off the top surface 240, hence finishing the whole ABS forming process.
During above slider ABS forming process, some problems arise. More specifically, due to limitation of technology, smoothness of the top surface of the slider substrate is generally low. Consequently, after the photo-resist is exposed and trenches are formed therein, edges of the trenches adjoining the top surface of the substrate will not be rigidly straight lines; on the contrary, they will become irregular in shape. For example, as shown in FIGS. 3a-3b, an irregular edge 266, for example a zigzagged edge of a sidewall 262 of a trench of a photo-resist 26 is produced at a location adjacent the substrate 219.
When performing subsequent ion milling/reactive ion etching process, the irregular edge 266 will cause re-deposition of substrate material on the substrate at location near the edge 266. In other words, substrate material at the location near the edge 266 will not be etched away as would be desired; adversely, it will be deposited once again on that location and as a bad result, fencing structure (re-deposition), which is higher than top surface of the substrate, is produced after the etching process is finished. As illustrated in FIGS. 4a-4b, a fencing region 224, which is higher than a top surface 240 of a slider 203 and adjacent a sidewall 222 of a recess (not labeled), is formed during etching process. The fencing structure negatively influences performances of the entire disk drive unit. For example, it will become difficult to further reduce flying height of the slider for achieving much larger data storage capability; moreover, the fencing structure will inevitably increase probability of scratches on the slider and/or disk, and in some extreme situations, this will result in serious crash of the disk.
On the other hand, during the photo-resist exposure process described above, because some light beam may be reflected from top surface of the substrate and scattered back into the photo-resist, polymerization reaction speed will be decreased gradually from top to bottom of the photo-resist, thus insufficient polymerization occurring at bottom of the photo-resist. As a result, when the photo-resist is developed, the sidewalls of the trenches are non-vertical, also known as “footing” (e.g. footing region 264 shown in FIGS. 3a-3b). Consequently, the ABS pattern in the photo-resist that is subsequently transferred to the substrate is not the desired pattern, but will have errors resulting from the photo-resist footing. For example, as shown in FIGS. 4a-4b, a sidewall 222 of a slider 203 is non-vertical due to reasons discussed above. This will cause bad dimension accuracy for the ABS thus formed, thereby degrading flying performance of the slider.
Therefore, there is a need for an improved design to overcome the prior art drawbacks.